Setting a C++ iterator to an "invalid" value?

[Josh]

Is there any way to set an iterator to a state or value that marks it as "invalid"? I end up storing a boolean member along with every iterator like "addedtoshadowcasterupdatelist". It would be a lot easier if I could set set iterator=0 when it is initialized or removed from a list.

[martyj]

It would be a lot easier if I could set set iterator=0 when it is initialized or removed from a list.

 

Are you referring to setting the iterators value = NULL?

 

Maybe something like this?

std::vector<Entity*> entities;
for(auto it = entities.begin(); it != entities.end(); it++)
{
if(condition)
{
 *it = NULL;
}
}

 

Idk if that would work, iterators are just pointers to each element. I'm not too proficient at my C++, more of a C, just a guess.

[f13rce]

He's referring to the iterator, not iterator value.

 

But you can you use the value of the iterator as a flag, although it can be dangerous in case an object or variable does have that value.

An alternative way could perhaps be using it = list.end(), as end() has no value assigned to it.

 

I don't really think there's a clean way to set it to "invalid" in any other way.

[Josh]

The problem with the list.end() method is you need a list to compare it to. Okay, create a global one. Now you need one for every single type of list that might exist!

 

I have never set the value of an iterator like that. Is that safe and portable?

[f13rce]

I've never tried it myself, so use it at your own risk I suppose...

[Rick]

t would be a lot easier if I could set set iterator=0 when it is initialized or removed from a list.

 

You're storing iterators in a list? What's the goal with this request? Why do you want to do that when it's initialized or removed from a list (still seems odd to store iterators in a list)?

[Josh]

No, I store list iterators for fast removal.